    #include <unistd.h>  
    #include <stdlib.h>  
    #include <stdio.h>  
    #include <string.h>
    #include <sys/shm.h>  
    #include <sys/ipc.h>
    #include <sys/types.h>
    #include "shmdata.h"  
      
    int main()  
    {  
        int running = 1;//程序是否继续运行的标志  
        void *shm = NULL;//分配的共享内存的原始首地址  
        struct shared_use_st *shared;//指向shm  
        int shmid;//共享内存标识符  
        //创建共享内存  
        shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);  
        if(shmid == -1)  
        {  
            fprintf(stderr, "shmget failed\n");  
            exit(EXIT_FAILURE);  
        }  
        //将共享内存连接到当前进程的地址空间  
        shm = shmat(shmid, 0, 0);  
        if(shm == (void*)-1)  
        {  
            fprintf(stderr, "shmat failed\n");  
            exit(EXIT_FAILURE);  
        }  
        printf("\nMemory attached at %ld\n", (long int)shm);  
        //设置共享内存  
        shared = (struct shared_use_st*)shm;  
        shared->written = 0;  
        while(running)//读取共享内存中的数据  
        {  
            //没有进程向共享内存定数据有数据可读取  
            if(shared->written != 0)  
            {  
                printf("You wrote: %s", shared->text);  
                sleep(rand() % 3);  
                //读取完数据，设置written使共享内存段可写  
                shared->written = 0;  
                //输入了end，退出循环（程序）  
                if(strncmp(shared->text, "end", 3) == 0)  
                    running = 0;  
            }  
            else//有其他进程在写数据，不能读取数据  
                sleep(1);  
        }  
        //把共享内存从当前进程中分离  
        if(shmdt(shm) == -1)  
        {  
            fprintf(stderr, "shmdt failed\n");  
            exit(EXIT_FAILURE);  
        }  
        //删除共享内存  
        if(shmctl(shmid, IPC_RMID, 0) == -1)  
        {  
            fprintf(stderr, "shmctl(IPC_RMID) failed\n");  
            exit(EXIT_FAILURE);  
        }  
        exit(EXIT_SUCCESS);  
    }  
